Start up costs: You’ll need to jump-start the open source community. Some minimal marketing, PR, and sales costs are likely before you get to critical mass.

Documentation: It will be easier to get adopters if they don’t have to read the source tree to figure out if it might be valuable to them. Existing documentation may need to be expanded, edited, or ported to a wiki.

Automated testing: As you add more developers, your need for automated testing increases, so you may need to add or enhance tests.

Oversight: Until you can recruit trusted open source partners, all outside check-ins must be vetted for bugs, utility, and foolishness.

These costs are small, but if no one joins your community, you’ll waste your company’s money.